Chrysler Repair: electrical issues, ee degree, turn signals

Question
Roland,
Thanks for the quick reply. (99 t&C starts in any gear). I am not sure how to check for short with wires connected at the 10 pin connector. I have a multi tester. Should vans battery be connected, key in "on position"? Running? In "R" or "N"? "P"? And when I disconnect the connector?
"Back-up" lights on in run position with fuse in place.

Answer
Hi John,
Below is the original q and a. For convenience please use the 'follow-up' option rather than starting a new question so we have a running dialog to refer to.

"Question:  I have a 1999 Chrysler T&C Limited. 3.8L, 2-wheel drive,4 speed auto. Van can start in reverse or drive. Reverse lights on when running any gear. Blows "bu/rev/abs" fuse when switching from P to D.  Blower won't work but Turn signals run but slow. I checked other fuses and when I removed "Gages" fuse turn signals stopped working. (Not sure if related but rear wiper motor hasn't worked and flat-4 tow cable been removed)I removed gage cluster and re-soldered some connections. I have read many similar letters but still need HELP. What am I missing (besides and EE degree in automotive)??? Please help!
Answer: Hi Big John,
I prefer to deal with one problem at a time and then go on to others so as to avoid confusion/exhaustion.
Lets start with the start in any gear and reverse lights 'on' in any gear, and the bu/rev/abs fuse blowing when switching from park to drive (but that would seem to disagree with the 'reverse lights 'on' in any gear?' because that fuse does power the bu lights). So which is it?
The issues you describe are mediated inside the transmission by the transmission range sensor switch which has a 10-pin plug at the transmission. The brown/yellow wire on pin 10 should show a short to ground, but only when the shift is in park or neutral. If it shows ground in any other positions then disconnect the plug and see whether the pin in trans side of the socket is showing the same thing or whether the brown/yellow wire at the plug side is showing a short to ground (which it shouldn't, and if it does then the wire is shorted somewhere between the plug and pin 76 if powertrain control module). One way or the other we have to get the always short to ground situation corrected if you want to prevent starting in all gear positions.
The fuse (also known as #12) also is connected to the trans range sensor switch at pin 1 white wire. When you shift into reverse that should apply 12v from pin 1 over to pin 6 violet/black wire and from there to the back up lamps and the automatic day/night mirror if you have that feature. Why the back ups are always on (or is the fuse blown?) could be a short between the two wires that by-passes the switch, or a short to ground of the white wire.
Maybe the first thing to do would be to look into the trans range sensor switch's socket on the transmission and also check the harness going to the plug at the socket and see if you find any abnormal/suspicious situation that would explain why you have these 'gremlins'.
Let me know when that is fixed, and then explain in greater detail each of the remaining problems (one question for each at a time, please). The chances are they are caused by different reasons rather than a single magic bullet so the details will be important for me to understand what might be the solution.
Roland"

Answer to this question:
The test I listed above is to be done at the 10-pin plug/socket on the trans, and begin with the plug removed from the socket.  Battery may remain connected, key off. You will find the pin numbers to be etched into the plug or simply look at the wires colors as a means of identifying the pin numbers on the socket side.  You don't want to have the key 'on' to do the ground/no ground tests with the gear shift in various positions, and 'ground' point for the meter lead could well be the negative post of the nearby battery or any piece of shiny chassis/engine metal. Similarly the test of a short in the wire on the plug side of the same pin 10 would be with the key 'off'.
The voltage measurement will have to be made with the key in the 'on' position, and either with the plug remove or not as needed. If the plug is inserted in the socket and you need to test for voltage on a specific wire you would insert a straight pin thruough the wire insulation so as to connect to the conducter and clip your meter lead to the straight pin.
As to the #12 fuse blowing when you switch from P to D, that probably happens when you go through the R position in that move. But why it does blow and then doesn't blow in any of the D positions and the lights stay 'on' is to be determined. Or am I mistaken about when it blows?
Roland

PS I note that you apparently read my first answer off of the home page, rather than by checking it out directly from the email the site sent you. You might want to do the direct reading as that cuts out the time delay until the posting of today's answers until tomorrow. And also that way you can send me a follow-up and we get it all linked together (past and present response). If you would care to rate/nominate my answer that is also available to you at that time.